Electronic systems



United States Patent ELECTRONIC SYSTEMS Edward C. Dench, Needham, Mass., assignor to Raytheon Company, a corporation of Delaware Application December 13, 1957, Serial No. 702,587

12 Claims. (Cl. 315-35) This invention is concerned with a system for increasing the band width of a traveling wave oscillator, given a minimum and maximum power level which should not be exceeded, or for increasing the tube power level rating for a given band width. 1

Traveling wave oscillators are known wherein an electron beam-generated by an electron gun including a cathode, a control grid, and an accelerating anodepasses through a magnetic field and an electric field transverse to the magnetic field. The electric field is produced by a voltage supplied between a slow-wave propagating structure, otherwise referred to as an anode delay line, and an auxiliary negative electrode, often referred to as a sole. Such oscillators may be tuned over a comparatively wide range of frequencies by varying the electron beam velocity, either through adjustment of the aforesaid voltage, or by adjustment of the transverse magnetic field strength, or both. The electron 'beam current in the tube may be adjusted in accordance with the grid voltage; such tubes are shown in a copending application of Edward C. Dench, Serial No. 391,628, filed November 12, 1953. The electron beam current is also a function of the electron gun accelerating anode voltage.

Present tunable high power traveling wave oscillators are restricted in their frequency tuning range by the fact that, for a substantially constant beam current, or for a beam current which rises slightly with anode voltage, the power input to the tube increases as the anode voltage and frequency increases. Consequently, anode dissipation at the anode becomes excessive if one attempts to operate at a frequency in excess of a predetermined limit. In order to prevent damage to the anode, it thus becomes necessary to avoid operating above a critical upper frequency limit at which this dissipation exceeds the capability of the tube. On the other hand, at the lower end of the tuning range the anode voltage is comparatively low, so that the power input and, consequently, the power output of the tube, is lower. If one operates such a tube so that the upper end of the tuning range does not exceed the dissipation limit, then the lower frequency limit of operation is restricted by the minimum power rating which one desires to assign to the tube. Because of the above characteristics of such a tube, that is, substantially constant beam current, one must either sacrifice band width to maintain a desired minimum power output rating, or sacrifice minimum power output rating for band width.

Pursuant to the invention, the voltage on the grid or accelerating anode, or both, of the electron gun of a traveling wave oscillator is synchronized with the variations of anode delay line voltage in such a manner that, as the anode delay line voltage increases, the grid voltage, or accelerating anode voltage, as the case may be, is so adjusted as to eifect a decrease in the beam current, and vice versa. In this way, substantially constant anode dissipation may be maintained over a much broader tuning band. Changes in anode delay line Volt- 2,924,740 Patented Feb. 9, 1960 age may be sensed by a control circuit which provides a control signal for affecting the electron beam current. It should be understood, however, that changes in beam current may be sensed by a control circuit for deriving a control signal which affects the accelerating anode voltage, or the control grid voltage, as the case may be.

The invention, along with its operating principles, will be more readily understood by referring to the accompanying drawings wherein:

Fig. l is a circuit diagram depicting an embodiment of a traveling wave oscillator control system; and

Fig. 2 is a circuit diagram of a modification of the system of Fig. 1.

Referring to Fig. 1, a traveling wave oscillator is indicated by the reference numeral 10 and includes an electron gun 12, a periodic slow wave propagating structure 14 to which an output energy coupling means 15 is coupled, and an elongated auxiliary electrode 16, commonly referred to as a sole. The traveling wave tube 10 is shown schematically and may be of any desired configuration, such as linear or cylindrical. Typical structures are shown in the aforesaid copending application. The electron gun 12 includes a cathode 17, an accelerating anode 18, and a control grid 19, which may be connected to the cathode, as shown in the system of Fig. 1. The cathode 17 is connected to the negative bus 21 which, in turn, is connected to the negative terminal of the direct current anode delay line voltage source 22. The sole 16 may be biased with respect to the cathode by means of the battery 24 connected between sole 16 and the negative bus 21. A series regulator tube 25 is inserted in the positive bus 26 which interconnects the positive terminal of the direct current anode voltage source 22 and the anode delay line 14 of tube 10. Thus the series regulator tube 25 is in series with the traveling wave tube across the supply terminals of the source 22. Shunt tube 31 is included in the circuit of Fig. 1 and includes a resistor 28 interconnecting the plate circuit of tube 31 and the cathode 32 of series regulator tube 25. The junction 34 of resistor '28 and the plate 33 of tube 31 is connected to the grid 35 of series regulator tube 25 by means of a lead 37. A voltage regulator tube 39, such as a neon lamp, is inserted between the cathode 38 of tube 31 and the negative bus 21 in order to maintain the cathode 38 of tube 31 at a constant potential value. The grid 41 of shunt tube 31 is connected to a variable tap 43 of an output resistor 42 which is connected between busses 21 and 26.

The grid potential of the shunt tube 31 is determined by the setting of the arm 43 of variable resistor 42. The arm 43 is set so that the grid voltage is less positive than the cathode by an amount of bias which causes the shunt tube to pass a certain plate current. This plate current flows through the plate load resistance 28 and causes a voltage drop thereacross. The magnitude of the voltage across resistor 28 is the bias on the series regulator tube 25. Therefore, adjustment of the variable resistor establishes the normal resistance of the series regulator tube. The plate-to-cathode resistance of series regulator tube 25 is in series with the resistor 42 and, together with the latter, constitutes a voltage divider across the terminals of the anode delay line voltage source 22. By varying the resistance of the series regulator tube, the voltage across the resistor 42that is, the voltage between the anode delay line and the sole-is varied. Thus, adjustment of resistor 42 determines the value of the anode delay line voltage and sets the frequency of operation of the traveling wave tube. The position of the tap 43 of resistor 42 determines the anode-to-sole voltage in a manner now to be described. If the tap 43 of resistor 42 is moved upward, the voltage at the grid 41 of shunt tube 31 relative to the cathode 38 becomes more positive. Since the potential of the cathode of the shunt tube 31 is held at a constant potential by the glow discharge tube 39, the shunt tube plate current increases. The increased plate current flowing through the plate resistor 28 of tube 31 causes an increased voltage drop across resistor 28. This voltage drop across resistor 28 serves as a bias voltage for series regulator tube 25; in other words, as the current through resistor 28 increases, the potential at the junction 34 becomes more negative and a decrease in plate current in the series regulator tube 25 results. The plate resistance of regulator tube 25 increases and a greater voltage appears across the increased resistance of the series regulator tube. Consequently, less voltage appears across output resistor 42 of the divider 25, 42, and the voltage between delay line 14 and sole 16 decreases. Similarly, it may be shown that if the tap 43 of resistor 42 is moved downward, the plate resistance of the series regulator tube will be decreased, more voltage will appear across output resistor 42 of the divider 25, 42, and the anode delay line voltage will increase.

A source 46 of accelerating anode voltage is indicated in Fig. 1; a seriesregulator tube 58 is connected in the positive bus 47 of this accelerating anode supply. The negative bus 48 may be connected to the negative bus 21 of the anode voltage source 22, or may be at the same potential. Also associated with the accelerating anode voltage source 46 is a shunt tube 51 and voltage regulator tube 52 interconnected between the cathode 53 of tube 51 and the negative bus 48. A resistor 55 is connected between the plate 54 of tube 51 and the cathode 57 of the series regulator tube 58. The junction 66 of resistor 55 and the plate 54 of tube 51 is connected to the grid 64 of series regulator tube 58 by way of lead 65. The junction 34 of resistor 28 and the anode 33 of tube 31 is connected by way of lead 59 to the grid 61 of tube 51 through a biasing battery 62. The output resistor 63 is connected between the positive and negative busses 47 and 48, respectively, of the accelerating anode power supply 46.

It will be assumed, for purposes of explanation, that the tap 43 of resistor 42 is moved upward so that the anode delay line-to-sole voltage of the traveling wave tube decreases, in the manner previously described. Movement of tap 43 of resistor 42 upward, as already explained, will cause the bias on shunt tube 31 to become more positive, the plate current through resistor 28 to increase, and the negative bias voltage across resistor 28 to increase. The increased negative bias voltage appearing at junction 34 is supplied by way of lead 59 to the grid 61 of the shunt tube 51 for the accelerating electrode direct current supply source 46 in series with the fixed bias from the battery 62. This increased negative bias voltage causes a decrease in the plate current of shunt tube 51 and a decreased voltage drop across plate resistor 55. This decreased voltage drop serves to bias the series regulator tube 58 less negatively and the plate resistance of series regulator tube 58 decreases. The voltage available across output resistor 63 thus increases. This voltage across resistor 63 appears between the accelerating anode 18 and the cathode 17 of the electron gun 12 of traveling wave tube 10. In other words, the accelerating anode voltage increases with decreasing anode delay line voltage. The effect of decreasing the accelerating anode voltage is to decrease the power input, as well as the power output, of the tube. Similarly, movement of tap 43 of resistor downward, which causes an increase in the anode delay lineto-sole voltage, causes the voltage of junction 34 to become more positive, whereupon the bias on the grid 61 becomes more positive, current flow in tube 51 increases, the voltage at junction 66 becomes more negative, tube 58 conducts less, the resistance of tube 58 increases and the voltage available across resistor 63 decreases. In other words, the accelerating anode voltage of the traveling wave tube 10 decreases as the anode delay line voltage increases. The relationship between the anode delay line voltage and the accelerating anode potential, the power input, or the power output, as the case may be, may be made linear or may follow any other function, depending upon the circuit design.

A modification of the system of Fig. 1 of the drawing is shown in Fig. 2, in which certain portions are omitted for the sake of simplification. In the system of Fig. 2, the output voltage existing across resistor 63 is connected by way of lead 47 to the control grid 19 of the traveling wave tube electron gun 12. The grid and cathode of Fig. 2, unlike those of Fig. 1, are not interconnected. The accelerating anode 18 of Fig. 2 is connected to a source of fixed positive biasing potential. The change in voltage across resistor 63, owing to variations in the anode delay line-to-sole voltage, now causes a variation in the electron gun grid voltage relative to the electron gun cathode 17. As is obvious from the explanation of the system of Fig. 1, a decreased output voltage across resistor 63 owing to an increase in anode delay lineto-sole voltage of the traveling wave tube, is accompanied by a decrease in the electron gun grid voltage. An increase in anode delay line-to-sole voltage is accompanied not only by a decrease in beam current but also by a decrease in power input and a decrease in power output. The relationship between anode delay line-tosole voltage and beam current (or power input or power output) may be made substantially linear or any other function depending on well-known principles of circuit design.

It should be noted that the systems of Fig. l or 2 also incorporate a voltage regulating feature which compensates for changes in voltage of either of the two power supplies 22 or 46. For example, if the voltage of anode voltage power supply 22 should tend to increase, the voltage existing across the entire voltage divider 25, 42 in parallel with the power supply 22 would also tend to increase. Obviously, the voltage across the resistor 42 of the voltage divider would tend to increase and, for a given position of arm 43, the bias on shunt tube 31 would increase in a positive direction. Because of the greater current in shunt tube 31, the plate voltage, i.e., the voltage at junction 34 would become more negative, the resistance of series regulator tube 25 would increase, and less voltage would appear across resistor 42. In other words, a tendency for the delay line-to-sole voltage to increase because of an increase in the voltage of source 22 would be oflset by a tendency for the anode delay line-to-sole voltage to decrease correspondingly. Likewise, any tendency for the anode delay line voltage to decrease owing to a drop in voltage of source 22 would be compensated for by a tendency for the voltage across element 42 of the voltage divider 25, 42 to increase.

The operation of the regulating circuit for the accelerating anode voltage supply 46 is obviously identical to that of the anode delay line voltage supply 22.

This completes the description of the embodiment of the invention illustrated herein. However, many modifications and advantages thereof will be apparent to persons skilled in the art without departing from the spirit and scope of this invention. Accordingly, it is desired that this invention not be limited to the particular details of the embodiment disclosed herein except as defined by the appended claims.

What is claimed is:

1. In combination, a traveling wave tube having a slowwave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio frequency fields of the wave energy being transmitted, an auxiliary electrode adjacent said structure, means for providing a unidirectional electric field between said structure and said auxiliary electrode in response to a potential difference existing between said structure and said auxiliary electrode, said potential difference being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electron gun for producing an electron beam and for directing said beam through said region in energy exchanging relation with said radio frequency fields, and means responsive to said potential difference and disposed in circuit with said electron gun for varying the magnitude of the electron beam current inversely with the magnitude of said potential difference.

2. In combination, a traveling wave tube having a slowwave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio frequency fields of the wave energy being transmitted, an auxiliary electrode substantially in juxtaposition with said structure, means for providing a unidirectional electric field between said structure and said auxiliary electrode in response to a potential difference existing between said structure and said auxiliary electrode, said potential difference being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electron gun for producing an electron beam and for directing said beam through said region in energy-exchanging relation with said radio frequency fields, and means responsive to the magnitude of said potential difference for varying the power input of said tube inversely with said potential difference.

3. In combination, a traveling wave tube having a slow-wave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio frequency fields of the wave energy being transmitted, an auxiliary electrode substantially in juxtaposition with said structure, means for providing a unidirectional electric field between said structure and said auxiliary electrode in response to a potential difference existing between said structure and said auxiliary electrode, said potential difference being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electron gun for producing an electron beam and for directing said beam through said region in energy-exchanging relation with said radio frequency fields, and means responsive to the magnitude of said potential difference for varying the power output of said tube inversely with said potential difference.

4. 'In combination, a traveling wave tube having a slowwave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio frequency fields of the wave energy being transmitted, an auxiliary electrode in juxtaposition with said structure, means for providing a unidirectional electric field between said structure and said auxiliary electrode in response to a potential difference existing between said structure and said auxiliary electrode, said potential difierence being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electron gun for producing an electron beam and for directing said beam through said region in energy-exchanging relation with said radio frequency fields, said electron gun including a beam current control electrode, means for obtaining a control voltage in accordance with the magnitude of said potential difference, and means responsive to said control voltage and disposed in circuit with said control electrode for causing the magnitude of the beam current to vary inversely as the magnitude of said potential difference.

5. In combination, a traveling wave tube having a slowwave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio frequency fields of the wave energy being transmitted, an auxiliary electrode in juxtaposition with said structure, means for providing a unidirectional electric field between said structure and said auxiliary elec trode in response to a potential difference existing between said structure and said auxiliary electrode, said potential difference being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electron gun for producing an electron beam and for directing said beam through said region in energyexchanging relation with said radio frequency fields, said electron gun including a beam current control electrode, means for obtaining a control voltage in accordance with the magnitude of said potential difference, and means responsive to said control voltage and disposed in circuit with said control electrode for causing the magnitude of the beam current to vary inversely as the magnitude of said potential difference, the relationship between the manner of variation of the beam current and that of said potential difference being substantially linear.

6. In combination, a traveling wave tube having a slowwave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio frequency fields of the wave energy being transmitted, an auxiliary electrode positioned adjacent said structure, means for providing a unidirectional electric field between said structure and said auxiliary electrode in response to a potential difference existing between said structure and said auxiliary electrode, said potential difference being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electron gun for producing an electron beam and for directing said beam through said region in energy-exchanging relation with said radio frequency fields, said electron gun including a control electrode and a cathode, control means for obtaining acontrol voltage in accordance with the magnitude of said potential difference, and means responsive to said control voltage and disposed in circuit with said control electrode for causing the potential of said control electrode relative to said cathode to vary inversely as the magnitude of said potential difference.

7. In combination, a traveling wave tube having a slow-wave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio frequency fields of the wave energy being transmitted, an auxiliary electrode positioned adjacent said structure, means for providing a unidirectional electric field between said structure and said auxiliary electrode in response to a potential difference existing between said structure and said auxiliary electrode, said potential difference being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electron gun for producing an electron beam and for directing said beam through said region in energy-exchanging relation with said radio frequency fields, said electron gun including a control electrode and a cathode, control means for obtaining a control voltage in accordance with the magnitude of said potential difference, and means responsive to said control voltage and disposed in circuit with said control electrode for causing the potential of said control electrode relative to said cathode to vary inversely as the magnitude of said potential difference, the relationship between the manner of variation of said control electrode potential and that of said potential difference being substantially linear.

8. In combination, a traveling wave tube having a slow-wave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio-frequency fields of the wave energy being transmitted, an auxiliary electrode substantially in juxtaposition with said structure, means for providing a unidirectional electric field between said structure and said auxiliary electrode in response to a potential difference existing between said structure and said auxiliary electrode, said potential difference being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electron gun for producing an electron beam and for directing said beam through said region in energy-exchanging relation with said radio-frequency fields, said electron gun including a control electrode and a cathode, control means for obtaining a control voltage in accordance with the magnitude of said potential difference, and means responsive to said control voltage and disposed in circuit with said control electrode for causing the power output of said traveling wave tube to vary inversely as the magnitude of said potential diiference.

9. In combination, a-traveling wave tube having a slow-wave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio-frequency fields of the wave energy being transmitted, an auxiliary electrode substantially in juxtaposition with said structure, means for providing a unidirectional electric field between said structure and said auxiliary electrode in response to a potential difference existing between said structure and said auxiliary electrode, said potential difference being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electrode, an electron gun for producing an electron beam and for directing said beam through said region in energy-exchanging relation with said radio-frequency fields, said electron gun including a control electrode and a cathode, control means for obtaining a control voltage in accordance with the magnitude of said potential difference, and means responsive to said control voltage and disposed in circuit with said control electrode for causing the power output of said traveling wave tube to vary inversely as the magnitude of said potential difference, the relationship between the manner of variation of said control electrode potential and said'potential difference being substantially linear.

10. In combination a traveling wave tube having a slow-wave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio-frequency fields of the'wave energy being transmitted, an auxiliary electrode substantially in juxtaposition with said structure, means for providing a unidirectional electric field between said structure and said auxiliary electrode in response to a potential difference existing between said structure and said auxiliary electrode, said potential difference being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electron gun for producing an electron beam and for directing said beam through said region in energy-exchanging relation with said radio-frequency fields, said electron gun including a control electrode for afiecting the electron beam current, means for supplying a unidirectional voltage to said control electrode which includes a variable impedance element, means for effecting an impedance variation of said element in accordance with said potential difference which causes the control electrode voltage to vary inversely as said potential difference.

11. In combination, a traveling wave tube having a slow-wave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio-frequency fields of the wave energy being transmitted, an auxiliary electrode substantially in juxtaposition with said structure, means for providing a unidirectional electric field between said structure and said auxiliary electrode in response to a potential difference existing between said structure and said auxiliary electrode, said potential difference being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electron gun for producing an electron beam and for directing said beam through said region in energy-exchanging relation with said radio-frequency fields, said electron gun including a control electrode for affecting the electron beam current, means for supplying a unidirectional voltage to said control electrode, a voltage divider network including a first impedance element and a second impedance element connected in series across said means for supplying, said second impedance element being connected in circuit with said control electrode, means for varying the proportionof said unidirectional voltage appearing across said second impedance element in accordance with a control signal dependent upon the magnitude of said potential difference, and means responsive to the voltage across said second element for varying the electron beam current of said tube inversely as said potential difference.

12. In combination, a traveling wave tube having a slow-wave propagating structure for transmitting electromagnetic wave energy and constructed to produce adjacent thereto radio-frequency fields of the wave energy being transmitted, an auxiliary electrode substantially in juxtaposition with said structure, means for providing a unidirectional electric field between said structure and said auxiliary electrode in response to a potential diiference existing between said structure and said auxiliary electrode, said potential difference being subject to variation, means for producing a magnetic field transverse to said electric field in the region between said structure and said auxiliary electrode, an electrode gun for producing an electron beam and for directing said beam through said region in energy-exchanging relation with said radio-frequency fields, said electron gun including a control electrode for affecting the electron beam current, means for supplying a unidirectional voltage to said control electrode, a voltage divider network including a first impedance element and a second impedance element connected in series with said first impedance element across said means for supplying, the impedance of said first impedance element being varied in accordance with a control signal dependent upon the magnitude of said potential difference whereupon a control voltage across said second impedance element is correspondingly varied, said control and electrode voltage being determined by the magnitude of said control voltage and varying inversely as said potential difference.

References Cited in the file of this patent UNITED STATES PATENTS 2,302,876 Malling Nov. 24, 1942 2,611,832 Lapostolle Sept. 23, 1952 2,617,964 Blayney Nov. 11, 1952 2,702,370 Lerbs Feb. 15, 1955 

